TT #22 · Parashas Vayeitzei · Passuk 28:22
And this stone that I have set up as a pillar shall be God’s house, and of all that You give me I will surely give a tenth to You.
Torah Temimah points to sources on maaser.
TT lemma: עשר אעשרנו לך.
English: From here [we learn] that our father Yaakov accepted upon himself the mitzvah of maaser, and from him the generations learned.
Derash on the verse (midrashic) — not a formal named middah of the 13. The vow of a tenth is treated as the patriarchal origin of maaser.
Yaakov voluntarily undertook the obligation of giving a tenth; later generations follow his example.